This invention relates generally to a twist tie feed device as used for tying a group or bundle of items. For example, celery, asparagus, broccoli and the like, and more particularly to a twist tie feed device utilizing an electric drive and simple gearing operation.
Prior art patents teach the development of machines which effectively apply a tie wire about products to protect those products in transit prior to retail sale. The tie is a malleable wire sandwiched between two strips of paper secured together, for example with adhesive, to form a flat ribbon. The ribbon may also consist of plastic ribbon having a narrow center stripe of greater height than the adjoining areas. After a snug loop of ribbon is formed around the product, the ends of the ribbon are clamped. These clamped ends are then rotated about a central axis producing a permanent twist in the tie ribbon whereby the loop and product are held together. In the known manner, the ribbon can be untwisted by the purchaser of the product and retwisted when it is desired to re-apply the ribbon. These procedures have become most familiar to consumers, with twist ties being used on many products, not only to hold the above mentioned products together, but to provide closure for paper and plastic bags containing foodstuffs and other items and in larger sized bags used for containing potatoes, onions, etc.
Many operational steps are required to apply a twist tie in the form of a wire/paper ribbon. In the past, complex machinery has been designed to effect performance. These machines as illustrated for examples, in U.S. Pat. No. 3,318,230 issued May 9, 1967; 3,428,096 issued Feb. 18, 1969; 3,898,924 issued Aug. 12, 1975 and U.S. Pat. No. 4,177,842 issued Dec. 11, 1979, are machine constructions relying on complex mechanisms, electrically driven in some instances, and generally using cam devices to provide sequential motions necessary to the procedural steps in applying a twist tie ribbon to the product. Each progressive patent teaches an improvement in performance and simplification in structure, however, endless belt chain drives, pulleys, complicated linkage systems are not uncommon and the need for adjustment for operation and to compensate for temperature variation and for wear is relatively frequent. Use of both a forward feed drive for the ribbon and also an independent reverse feed drive for tightening the ribbon about the bundle is also disclosed in the prior art, adding to complexity.
It is also known from U.S. Pat. No. 4,559,977 issued on Dec. 24, 1985 to provide a pneumatic twist tie feed device for providing a helical wrap about the package. This device utilizes a first gripper which clamps and retains the free end of the ribbon against a second gripper. Pressure rollers operate in reverse retracting excess ribbon about the produce. A friction clutch, operative only for reverse ribbon feeding, allows for ribbon slippage as the ribbon tightens around the produce. Then the second gripper clamps the other end of the ribbon against the twister head and a twister mechanism rotates the clamped ends of the ribbon about a common axis twisting the ribbon ends together. Axial gripper motion is provided by cylindrical valves having pistons concentric with and supported by a gripper support rod tube and acting, respectively at the ends of the gripper supports away from the tie ribbon. A rack and pinion mechanism is used to provide rotation of twister mechanism and forward and reverse feeding of the ribbon. All components are pneumatically driven.
This prior art device was satisfactory. However, it also was overly complex requiring the simultaneous control of several pneumatic valves and solenoids. Additionally, because the ring was a helical ring, if the helical wrap became shifted to be perpendicular to the bundle, the wrap became loose. Additionally, only a single forward drive wheel was utilized in conjunction with an idler so that during reverse driving, the idler must be removed from contact with the ribbon, while an accumulator rod was utilized to pull and tension the ribbon in a backward feeding direction.
What is needed is a twist tying machine which is simple and reliable in construction, and reduces the total number of parts, which provides a circular wrap and may perform wrapping without the use of an accumulator.